shell 的一些条件判断

xiahe999

　　1. shell判断文件,目录是否存在或者具有权限
　　2. #!/bin/sh
　　3.
　　4. myPath="/var/log/httpd/"
　　5. myFile="/var /log/httpd/access.log"
　　6.
　　7. # 这里的-x 参数判断$myPath是否存在并且是否具有可执行权限
　　8. if [ ! -x "$myPath"]; then
　　9. mkdir "$myPath"
　　10. fi
　　11.
　　12. # 这里的-d 参数判断$myPath是否存在
　　13. if [ ! -d "$myPath"]; then
　　14. mkdir "$myPath"
　　15. fi
　　16.
　　17. # 这里的-f参数判断$myFile是否存在
　　18. if [ ! -f "$myFile" ]; then
　　19. touch "$myFile"
　　20. fi
　　21.
　　22. # 其他参数还有-n,-n是判断一个变量是否是否有值
　　23. if [ ! -n "$myVar" ]; then
　　24. echo "$myVar is empty"
　　25. exit 0
　　26. fi
　　27.
　　28. # 两个变量判断是否相等
　　29. if [ "$var1" = "$var2" ]; then
　　30. echo '$var1 eq $var2'
　　31. else
　　32. echo '$var1 not eq $var2'
　　33. fi
　　-f 和-e的区别
　　Conditional Logic on Files
　　-a file exists.
　　-b file exists and is a block special file.
　　-c file exists and is a character special file.
　　-d file exists and is a directory.
　　-e file exists (just the same as -a).
　　-f file exists and is a regular file.
　　-g file exists and has its setgid(2) bit set.

　　-G file exists and has the same group>　　-k file exists and has its sticky bit set.
　　-L file exists and is a symbolic link.
　　-n string length is not zero.
　　-o Named option is set on.

　　-O file exists and is owned by the user>　　-p file exists and is a first in, first out (FIFO) special file or
　　named pipe.
　　-r file exists and is readable by the current process.

　　-s file exists and has a>　　-S file exists and is a socket.
　　-t file descriptor number fildes is open and associated with a
　　terminal device.
　　-u file exists and has its setuid(2) bit set.
　　-w file exists and is writable by the current process.
　　-x file exists and is executable by the current process.
　　-z string length is zero.
　　是用 -s 还是用 -f 这个区别是很大的！